The immediate goal of this research is the development of improved methods of serological tests for C. trachomatis genital infection, i.e., NGU, the most common venereal disease in the U.S. and European countries. The long-term goal is the elucidation of immunopathogenesis of C. trachomatis genital infection. The goal is approached through the development of improved serological methods for diagnosis and detection of serum and local antibodies, and the studies in humans of humoral immune response using various chlamydial antigens and cellular immune response using peripheral blood lymphocyte blast transformation, and the studies of cellular immune mechanisms using cultured mouse peritoneal macrophages.